There are a number of processing adjustments which can be made in Adobe Photoshop to enhance your CCD images (and almost all of these same techniques can be applied to film or digital astrophotos as well).  The basic techniques used are cloning, levels, curves, color balance, saturation, and cropping.  Cloning allows you to remove artifacts from an image such as dead pixels or satellite trails (or dust specks in a film image).  Levels and curves essentially change the brightness of different areas of an image, enhancing details.  Color balance determines the intensity of each color in an image and often needs to be adjusted based on the color sensitivity of a particular CCD camera.  Saturation is the intensity of the color in an image, often an overused processing routine, but very useful if applied appropriately.  Cropping allows you to throw out any unwanted portions of the image, especially places where multiple images do not line up correctly when overlaid.

When all is said and done we will have turned this image...

into this...

Cloning

It is usually best to remove any artifacts from an image before continuing with other processing routines.  Take a look at the image below which has several dead-pixel spots circled.  These are normal artifacts to see in a CCD image, especially from a large-format chip (one with several million pixels).

To remove these spots, use the Healing Brush tool.  This tool lets you duplicate an area of the image and paste it over the artifact you wish to remove.  Many dead pixels will be among the sky background, making them relatively easy to eliminate.  Previous versions of Photoshop required the use of the Clone tool, which worked well, but the Healing Brush is an incredible tool which makes it extremely simple to remove artifacts.

Choose a brush size a bit larger than the size of the spots you wish to remove.  If you select a stamp too large you will have a hard time avoiding objects you wish to keep or avoid cloning (like stars).  If you select a stamp too small it will take forever to remove all the spots!

Begin by selecting the Healing Brush Tool from the toolbar (or keyboard shortcut J).

Select the appropriate brush size and type from the Brush pulldown menu.  You can also use the bracket keys [ ] to increase or decrease brush size while working.

Take note of the region around the spot you want to remove and find a nearby area to clone.  Hold down the Alt key and click the area you wish to clone.  Now when you click on the artifact it will be replaced initially with the cloned area.  This was the limit of what the old Clone Tool could do, so the cloned area had to match the area it was pasted to very well.  With the Healing Brush, the newly replaced area is automatically matched to the surrounding pixels in color and brightness.  This is a spectacular tool which can save tons of time on a large image.

Below is the image after cloning out all the artifacts.

Next, Adjusting Levels...

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